1. Field of the Invention
The invention relates in general to a magnetron sputtering cathode mechanism, and more particularly to a magnetron sputtering cathode mechanism using a magnetic component to combine a target and a backing plate together and heighten the magnetic field to be close to a bombarded surface of the target.
2. Description of the Related Art
In the mechanical, electronic or semiconductor industry, in order to provide a specific feature to materials for being further used, a thin film is formed on surfaces of the materials by various methods. The sputtering method, which can be applied to the surface treatment of decorations, dining utensils, knives, tools, molds and semiconductor elements, is one of the most popular methods at present. The sputtering method is generally referred to a process of forming a thin film with the same or different materials on surfaces of various metal materials, hard alloys, ceramic materials and wafers so as to obtain elegant, wearproof, heat-resistant and corrosion-resistant features.
A magnetron sputtering apparatus, which can be adopted in various research fields, such as the electric machinery field, the mechanism field, the electronics field, the optics field or the material field, is a device for implementing the thin film sputtering process. The magnetron sputtering apparatus is based on the ion beam sputtering theory. When positive ions accelerated by the electrical filed impact a target bombarded surface, atoms and molecules of the target bombarded surface eject from the target bombarded surface after exchanging the kinetic energy with the high energy positive ions. This phenomenon is called “sputtering.”
The electrical filed is used in the magnetron sputtering apparatus to generate electrons between two electrodes. The accelerated electrons collide with inert gas (such as argon (Ar)) filled in the coating chamber in advance, so that the inert gas carries positive charges. The ions carrying the positive charges are attracted by the cathode in the magnetron sputtering apparatus to collide with the atoms of the target bombarded surface. The atoms obtain the kinetic energy from the incident ions because of being collided with the positive ions, so that the atoms under the target bombarded surface are forced to move. The displacement of several layers of the atoms under the target bombarded surface generates a reaction force perpendicular to the target bombarded surface to collide the atoms located at the target bombarded surface, so that the atoms scatter out. The scattered atoms (also collide with the neutral Ar atoms in the way to render the Ar atoms carry positive charges) eventually deposit on the substrate (the anode) to form a thin film. A set of magnets is added into the magnetron sputtering apparatus. The electron movement would be affected by the electromagnetic force generated by the electromagnetic effect between the magnetic field and the electrical field. If the magnetic direction is perpendicular to the electrical direction, the movement distance of the electrons lengthens as the electrons move in a spiral movement. As a result, the additional collision times of the electrons and the inert increase the probability for the inert gas to become the ions with positive charges. Thus, the depositing rate of the thin film increases.
In a magnetron sputtering cathode mechanism of the traditional magnetron sputtering apparatus, the target is usually fixed on the backing plate by using a backing plate bonding mechanism or a clamp holding mechanism. The target is directly adhered on the backing plate through adhesives by using the backing plate bonding mechanism. The way for fixing the target on the backing plate by the clamp holding mechanism will be illustrated with the appended figures in the following.
Referring to FIGS. 1A˜1B, a top view and a lateral cross-sectional view of a traditional magnetron sputtering cathode mechanism are illustrated, respectively. As shown in FIGS. 1A˜1B, the magnetron sputtering cathode mechanism includes a backing plate 11, a target 12, at least one magnet 14 and at least one clamp 15. The target 12 is held on the front surface of the backing plate 11 by the clamp 15, so that a bombarded surface of the target 12 faces backward the backing plate 11. The clamp 15 is fixed on the backing plate 11 or the cathode by the cooperation between its own hole and a screw. The magnet 14 disposed at a back surface of the backing plate 11 is used for providing a magnetic field.
However, the backing plate bonding mechanism and the clamp holding mechanism adopted in the described traditional magnetron sputtering cathode mechanism have shortcomings as follows:
1. When the target is changed by using the backing plate bonding mechanism, the backing plate with the remaining target has to be removed from the cathode. Then, another backing plate to which a new target is adhered is installed on the cathode. As a result, the installation is time-consuming and complicated.
2. As the backing plate on the cathode has to be usually changed by the backing plate bonding mechanism, the leak probability of the vacuum chamber is increased due to the installation defects. In addition, the leak detect has to be performed every time after the backing plate is changed.
3. While the backing plate bonding mechanism is used, the equipment and the process for bonding the target are used firstly to debond the remaining target from the backing plate and are used afterwards to bond a new target on the available backing plate.
4. While the backing plate bonding mechanism is used, more backing plates have to be prepared for bonding with the target except the backing plate installed on the cathode. Therefore, the equipment cost increases.
5. For the clamp holding mechanism, the manufacturing cost and the difficulty of maintaining and cleaning the clamp increase if the materials of the target and the clamp are the same (such as the process adopted ceramic materials to be the material of the target).
6. For the clamp holding mechanism, the deposited thin film is polluted by the bombarded clamp if the material of the clamp is aluminum or stainless steel metal which has lower manufacturing cost and is easy to clean and maintain.
7. For the clamp holding mechanism, as the deposited thin film polluted by the bombarded clamp is taken into the consideration, the bombarded area of the target is disposed away from the clamp when the cathode and the magnetic field are designed. Thus, a bombarded area of the target becomes narrow, so that the depositing rate is reduced and the dimension of the substrate is shrunk concurrently.
8. For the clamp holding mechanism, as the bombarded area of the target becomes narrow, the utilization rate of the target reduces.
9. For the clamp holding mechanism, screws are generally used to fix the clamp at the backing plate or the cathode, and it is not easy to well control the screws to be fastened tightly or loosely. If the screws are fastened too tightly, the target may be broken due to the heat expansion. If the screws are fastened too loosely, the target and the backing plate are ill-contacted, so that the heat within the target fails to transfer to the backing plate for cooling the target.
10. While the backing plate bonding mechanism or the clamp holding mechanism is used, the magnet is located under the backing plate. Thus, the distribution of the magnetic field above the target is not well and the magnetic field is weak, hence it is not easy to effectively control the electrons to collide with the inert gas.